We are requesting support to purchase an IBM SP-3 Night Hawk 1 parallel computer. This computer will be used by a core group of 5 major users at the Johns Hopkins University School of Medicine and Whiting School of Engineering. A total of 10 projects are proposed. These projects are supported by a total of ten RO1, one R37, and one PO1 NIH awards. Three of the major users are principal investigators on four of these awards. One major user is a Co-Principal investigator on four of these awards. The scope of the projects are broad, and include: a) an experimental and modeling study of the basis of arrhythmia in heart failure; b) computational modeling of cardiac sodium channel structure and function; c) computational modeling of metabolic oscillations in cardiac ventricular cells; d) computational modeling of blood flow and molecular transport in the microcirculation; e) computational modeling of mechanics and electromotility of the cochlear outer hair cell; f) computational mapping of brain structure and function. These projects have several features in common. First, each modeling study is linked closely to the underlying biology of the system being studied. Second; because the models being developed incorporate a high degree of biophysical and structural detail, they are computationally demanding. Consequently, each of the researchers in this proposal have previously used parallel computing to solve their respective problems. However, problem size has grown sufficiently that existing resources can no longer meet the needs of this group. Award of this instrument will have an immediate and direct stimulating effect on each of these projects. It will also enhance the ability of the Whitaker Biomedical Engineering Institute at Johns Hopkins University and the Department of Biomedical Engineering to play a leadership role in the field of computational modeling of complex biological systems at the local, national, and international levels.